Giant landslide inventory of Patagonia classified with the convolutional neural network AlexNet

We used the convolutional neural network AlexNet to detect giant landslides (>10^8 m³) along basaltic plateaus in the Patagonian extra-Andean region east of the Andean Cordillera (40°S-53°S, 66°W-72°W). The network was trained using topographic information (elevation, roughness, curvature) from TanDEM-X data. The dataset includes the original raster dataset as well as a polygon dataset. Since the network was trained with terrestrial data, large water bodies, the ocean as well as human settlements are sometimes detected as landslides. We removed the falsely predicted landslides patches in the polygon file of the dataset. Using artificial intelligence can help to analyze large quantities of data within a short time. The dataset shows are widespread landslides in the region are and how they might have been underestimated in their size and number in landslide inventories

Chronology and sedimentary characteristics of rock avalanches from Meseta Belgrano to Lago Pueyrredón Valley, Patagonia

&amp;lt;p&amp;gt;On the northern slopes of Meseta Belgrano (MB), eastern foothills of Patagonian Andes in Argentina, complex of multiple overlapping rock avalanches and landslides can be found. Interpretation of remote-sensing data, field mapping, together with OSL dating of lacustrine sediments revealed that slope collapses evolved during last oscillations of the Patagonian Ice Sheet and after its retreat. The longest rock avalanche with ~11 km runout originated most likely before the last glacial advance following the LGM because it involves moraine deposits in part of the scarp area. We suppose, that the distal part of the rock avalanche body was subaqueous due to presence of a proglacial lake in Lago Pueyrred&amp;amp;#243;n Valley after LGM. The hummocky character of the distal body and its lithological composition coming from MB bedrock was preserved, but the deposit is discontinuous with straight east-west glacial lineations on the surface. We think this is result of erosion by the ice sheet approaching from East during post-LGM glacial fluctuations. Next pronounced landslide activity took place after ~17 ka BP, when at least three rock avalanches overlaid lacustrine sediments in a dropping proglacial lake. One of them, superimposing the above described older rock avalanche, evolved from the collapsed moraine deposit and created ~5 km long lobe with subaqueous radial distal part. In the proximal parts of the rock avalanches east from this form, bellow the slopes of MB, distinct large ridge-like forms are visible in topography. They are similar to moraine ridges preserved on the MB slopes in higher altitudes. They can be interpreted as lower-lying moraines, but this requires another pronounced ice-sheet oscillation after its final retreat, which was not documented in Patagonian Ice Sheet chronostratigraphy. Thus, we interpret them as Toreva blocks. Documentation and granulometric analysis of natural outcrops in rock avalanche bodies show that typical features, i.e. blocky, jigsaw and fragmented facies are present throughout the depth along whole travel distances of rock avalanches. Fragmented facies with jigsaw-fractured blocks and preserved original lithology sequence are most frequent. Sedimentary facies are very similar in all of the studied rock avalanches, which collapsed from bedrock MB slopes, regardless of their age or size.&amp;lt;/p&amp;gt;</jats:p

Large rock avalanches into a glacial lake(s): a new chapter of the Patagonian Ice Sheet story

&amp;lt;p&amp;gt;Although ice retreat is widely considered to be an important factor in landslide origin, many links between deglaciation and slope instabilities are yet to be discovered. Here we focus on the origin and chronology of an exceptionally large landslides situated along the eastern margin of the former Patagonian Ice Sheet (PIS). Accumulations of the largest rock avalanches in the former PIS territory are concentrated in the Lago Pueyrred&amp;amp;#243;n valley at the eastern foothills of the Patagonian Andes in Argentina. Long-runout landslides have formed along the rims of sedimentary and volcanic mesetas, but also on the slopes of moraines from the Last Glacial Maximum. At least two rock avalanches have volumes greater than 1 km&amp;lt;sup&amp;gt;3&amp;lt;/sup&amp;gt; and many other landslide accumulations have volumes in the order of tens to hundreds of million m&amp;lt;sup&amp;gt;3&amp;lt;/sup&amp;gt;. Using cross-cutting relationships with glacial and lacustrine sediments and using OSL and &amp;lt;sup&amp;gt;14&amp;lt;/sup&amp;gt;C dating, we found that the largest volume of landslides occurred between ~17 and ~11 ka BP. This period coincides with a phase of rapid PIS retreat, the greatest intensity of glacial isostatic uplift, and a fast dropping of the glacial lakes along the foothills of the Patagonian Andes. The position of paleoshorelines in the landslide bodies and, in many places, the presence of folded and thrusted lacustrine sediments at the contact with rock avalanche deposits indicate that the landslides collapsed directly into the glacial lake. Although landslides along the former glacial lobe of Lago Pueyrred&amp;amp;#243;n continue today, they are at least an order of magnitude smaller than the rock and debris avalanches that occurred before the drainage of the glacial lake around 10-11 ka BP. Numerical modeling results indicate that large postglacial landslides may have been triggered by a combination of rapid sequential glacial lake drawdowns and seismicity due to glacial isostatic adjustment. We conclude that in addition to direct links such as glacial oversteepening, debuttressing and permafrost degradation, the retreat of ice sheets and the subsequent formation of transient large glacial lakes can fundamentally alter slope stability, especially if the slopes are built by weak sedimentary and volcanic rocks.&amp;lt;/p&amp;gt;</jats:p